On the Relationship Between Unsteady Forces and Shock Angles on a Pitching Airplane Model

A series of supersonic visualization tests were performed on an airplane model in both static and dynamic pitching cases. After image processing, the wave angles originating from different parts of the model were carefully measured and averaged over several oscillation cycles. These findings were then compared with the corresponding normal force under similar conditions. The results reveal a hysteresis loop in variations of the model shock angles with instantaneous angles of attack during up-stroke and down-stroke motions. In comparison with the normal force hysteresis loop, it has been found that there is an interesting relationship between the shape of the hysteresis loop of the shock angle and the corresponding loop observed in the normal force data. Further, the oscillation frequency has been shown to have similar e ects on both shock angle and aerodynamic force variations with the instantaneous angle of attack.